Friday, August 10, 2012
During our Bioblitz event on the 21st July 2012 we invited several expert surveyors in to see what exciting species they could find. The event was a huge sucess and we managed to record over 1,000 species in 24 hours, but what can these species tell us about the environment we live in?
On the day Mark Powell was looking at lichens around Woodwalton Fen and The Wildlife Trust Countryside Centre. Lichens have been used since the last century as indicators of air quality. Their use as an air quality meter was first discovered when they disappeared from the trees of England after the Industrial Revolution which caused increased acidity in rain. Different species of lichen will grow under different atmospheric conditons so the species of lichen growing can tell us what the quality of our air is like.
Mark managed to record some notable lichen species and commented on what the species he did find can tell us about our atmosphere today. Mark commented;
"Part of the excitment of studying lichens in lowland England is to observe the rapid re-colonization which has followed the decline of atmospheric sulphur dioxide pollution in recent decades. This pollution severly limited the range of lichens which could survive over most of England from the height of the Industrial Revolution through to the 1970's. The re-colonization got underway in the 1980's and continues today."
Sulphur dioxide is one of the pollutants that causes acid rain and is released from the combustion of fossil fuels like coal and oil. Since the Industrial Revolution emissions of Sulphur Dioxide increased, UK emissions peaked in the 1960s but have since declined by over 80%.
Lichens such as Arthonia radiata and Rinodina sophodes are now spreading rapidly in East Anglia and were found at the Bioblitz. Mark also commented;
"If Woodwalton Fen had been visited in the 1970's the most common licehn on the trees and shrubs would have been Leconora conizaeoides. This species was unusual in being favoured by atmospheric sulphur dioxide pollution. L.conizaeoides is now much less common and none was found on the bark or trees of Woodwalton Fen. The only place that it appears to be present is the chemically treated timber of Jackson's Bridge at the entrance to Woodwalton Fen.
Jackson's Bridge is one of the most exciting parts of the Fen for the lichenologist. Over twenty confirmed species have been recorded from the woodwork and there are several tantalising specimens which remain unidentified."
Mark also found that the concrete stilts of the Rothschild bungalow support some small colonies belonging to the Caloplaca citrina group. A recent review of the group using genetic fingerprinting methods has led to a much better understanding of this group. The material on the bungalow stilts can now be assigned to C.limonia (which ha sonly just been accepted as a British species) and to an un-described species which is temporarily labelled C.aff.austrocitrina.
Lichens are mysterious organisms, are biologically fascinating and come in a dazzling array of colours and sizes. A lichen consists of two or more partners that live together symbiotically, with both of them benefiting from the alliance. One partner is a fungus. The other is either an alga (usually a green alga) or a cyanobacterium, which is sometimes called a blue-green alga although it is more closely related to bacteria than algae.
The alga or cyanobacterium is able to use sunlight to produce essential nutrients by photosynthesis that feed both partners. The fungus creates a body, called a thallus, in which they both live. The fungus also produces chemical compounds that may act as sunscreen to protect the photosynthetic partner.
There are about 30,000 species of lichen worldwide, and they come in a dazzling variety of shapes and colours. Some are almost invisible to the naked eye and grow as a crust on rocks, trees or soil. Others are called beard lichens and these can be bushy or trailing.
Why not have a look in your own garden or park and see what lichens you can find. What can they tell you about the atmosphere around you?